Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

Good morning, fellow Foolish investors! Let's take a look at three companies which could make health care headlines this morning -- Johnson & Johnson , The Medicines Company , Santarus , and Tesaro .

Johnson & Johnson wins a positive opinion for Sirturo in Europe

Over the weekend, Johnson & Johnson announced that it received a positive opinion in the EU for its drug Sirturo, as part of a combination therapy for treating pulmonary multi-drug resistant tuberculosis in adults. The FDA approved Sirturo in December 2012 for the same indication.

While the positive opinion of the Medicinal Products for Human Use (CHMP) bodes well for an eventual European approval, investors should remember that the FDA approval of Sirturo was a controversial one. Critics pointed out that the FDA ruling was based on sputum cultures rather than overall patient deaths.

The CHMP opinion was based on positive data from a 24-week phase 2 clinical study in safety and efficacy of Sirturo versus a placebo, but it remains to be seen if similar concerns from the U.S. approval will arise ahead of its European approval.

Sirturo is notably the first new tuberculosis drug to be approved in over 40 years. However, annual peak peak estimates are modest, at $300 million -- which would only make it worth 1% of the pharmaceutical segment's top line, based on J&J's 2012 revenue of $25.4 billion.

The Medicines Company receives marketing authorization for cangrelor in Europe

Meanwhile, The Medicines Company announced that the European Medicines Agency (EMA) had accepted its marketing authorization application (MAA) for cangrelor. This is the second piece of good news regarding cangrelor this year, following the FDA's acceptance of its new drug application (NDA) in July.

Cangrelor is an investigational intravenous antiplatelet agent (blood thinner). Cangrelor is notably an active drug that does not require metabolic conversion, unlike Bristol Myers-Squibb's prodrug Plavix. Cangrelor has had a rocky past -- two phase 3 trials were halted in 2009 due to poor interim results.

After those failures, the company continued testing the drug as a possible treatment for short-term use prior to surgery. Cangrelor is currently in development for patients undergoing percutaneous coronary intervention (PCI) and patients who require bridging from an oral antiplatelet therapy to surgery. If approved, analysts believe cangrelor could generate annual peak sales of $400 million by 2019.

The Medicines Company's revenue mostly comes from U.S. sales of Angiomax, another blood thinner which generated 79% of the company's top line last quarter. U.S. sales of Angiomax rose 12% year-over-year to $138.5 million last quarter, boosting the company's net revenue by 27%.

Earlier today, Santarus announced that it had begun a phase 2a study of SAN-300, an investigational humanized monoclonal antibody, for the treatment of patients with active rheumatoid arthritis. The randomized, double-blind, and placebo-controlled trial will include 90 patients in 5 cohorts.

The administered doses will ascend from 0.5 mg/kg weekly to 4.0 mg/kg every other week. Each patient will receive 6 weeks of exposure to either SAN-300 or a placebo, and receive a 4 week follow-up checkup to assess the drug's overall safety and efficacy.

Santarus has high hopes for SAN-300 beyond rheumatoid arthritis. The company believes that the drug also has possible applications in other autoimmune diseases, inflammatory bowel disease, psoriasis, asthma, and organ transplantation.

Santarus currently has five marketed products -- Uceris, Zegerid, Glumetza, Cycloset, and Fenoglide. Of these drugs, Glumetza, a diabetes drug which helps control blood sugar in type 2 diabetes, generates the most revenue. Glumetza sales, at $45.6 million last quarter, accounted for 46% of the company's top line.

Investors should remember that Salix Pharmaceuticals has already agreed to acquire Santarus for $2.6 billion in November -- a transaction that will close in the first quarter of 2014. Therefore, any positive developments at Santarus should be considered good news for Salix as well.

Tesaro announces positive phase 3 results for Rolapitant

Last but not least, Tesaro just announced positive phase 3 data for Rolapitant, a drug for chemotherapy-induced nausea and vomiting.

Rolapitant had achieved its primary endpoint of a complete response over a delayed period of 24 to 120 hours, following the initiation of chemotherapy. Rolapitant was successful at treating both patients receiving moderately emetogenic and highly emetogenic chemotherapy. This bodes well for Tesaro's plans to submit an NDA to the FDA by mid-2014. If approved, Rolapitant could generate annual peak sales of $300 million.

Tesaro doesn't currently have any marketed products. Its product pipeline consists of three main drugs -- Rolapitant, Niraparib (breast and ovarian cancer), and TSR-011 (ALK+ mutations in non-small cell lung cancer). Rolapitant and Niraparib are currently farther along, in phase 3 trials, while TSR-011 is still in phase 1/2 trials.

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Fool contributor Leo Sun has no position in any stocks mentioned. The Motley Fool recommends Johnson & Johnson. The Motley Fool owns shares of Johnson & Johnson. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.